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### 22 Cards in this Set

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 Motional emf The separated charges on the ends of the moving conductor give rise to an induced emf called a motional emf because it originates from the motion of charges through a magnetic field. Emf exists as long as the rod moves. Electomagnetic induction The phenomenon of producing an induced emf with the aid of a magnetic field. Induced current and induced emf Changing the magnetic field induces an emf in the coil, and the emf leads to an induced current. How to created an induced emf? Changing the magnetic field and changing the area of a coil Magnetic flux Is proportional to the number of field lines that pass through a surface. Ways to change a magnetic flux? Change the angle Change the strength of magnetic field Change the area Lenz's law The induced emp is always in a direction such that the induced current will produce a flux which opposes the original change in flux. Mutual inductance The effect in which a changing current in one circuit induces an emf in another circuit. Because of the change in flux, an emf is induced in a secondary coil. Self-inductance The effect in which a changing current in a circuit induces an emf in the same circuit. Transformers Is a device for increasing or decreasing an ac voltage. A transformer that steps up the voltage simultaneously steps down the current, and a transformer that steps down the voltage steps up the current. What constitutes an alternating circuit? Flow of charge, surging back and forth. The charge flows continously in an ac circuit containing a capacitor. Relationship between resistance and frequency in ac voltage or current. Resistance R has the same value for any frequency of the ac voltage or current What is capacitive reactance? Determines how much rms current exists in a capacitor in response to a given rms voltage across the capacitor. Capacitive reacatance is inversely proportional to the frequency f of the voltage. Will a DC and AC current flow through a capacitor? A DC current will not flow through a capacitor. An AC current will flow through a capacitor. The current in a capacitor The current in a capacitor leads the voltage by a phase angle of 90. Current capacitor No power is dissipated, capacitor consumes no power Inducatance DC current will flow through an inductor. Ac current will flow through an inductor but self inductance causes a back emp which opposes changes in a current. Current in an inductor Current in an inductor lags behind the voltage by a phase angle 90. No power is dissipated. Circuits containing resistance, capacitance, and inductance? RCL Inductive reactance and frequency Directly proportional Impedance In a series RCL circuit the total opposition to flow is called the impedance. When does Resonance occur? When the frequency of vibrating force exactly matches a natural (resonant) frequency of the object to which the force is applied.